For a writer whose first book was a travelogue around small-town India, Pankaj Mishra seems strangely unwilling to engage with the complexities, or provincialities, of the United States. In his recent scathing review of Harvard historian Niall Ferguson’s book Civilisation: The West and the Rest, as in his other writings, Mishra seems interested in America only to the extent that he can caricature its ruling elite in order to knock them down, says Ethan Casey